Sometimes the best addition to a building involves the act of simple subtraction. Don’t top off, open up. Emphasize — or reveal — the virtues of what has been there all along.

Which is an elaborate way of describing how a modest building at the foot of Potrero Hill is poised to begin not its second life but its third. And the restoration is centered on a naturally ventilated atrium that did not exist before.

“We knew we wanted a space that felt like a greenhouse, so we played with different concepts and then thought, ‘Why not create one?’” said Mallory Shure, a senior project architect with Pfau Long Architecture.

The space Shure describes is now the hole in the doughnut of what’s being called the McClintock Building at 1400 16th St., an easy-to-miss stretch of San Francisco between the Mission and Mission Bay. The name pays homage to dress designer Jessica McClintock, who in the 1970s purchased a chemical plant from 1938 — stubby art deco, complete with a blunt faceted tower — and made it the home of her fashion empire, on a block then far from the downtown action.

Now retired, McClintock sold the building in 2014 to a development team headed by SKS Partners. It opens this spring and is leased to a single tenant, Invitae, a genetic testing firm whose work is as emblematic of the small area’s current character — heavy on tech and medical research, as the prior owners captured the tenor of their own times.

New on the inside

As restored by Pfau Long for SKS and its partners ProspectHill Group and ASB Capital, the McClintock name lives on in the logo on the structure’s 1957 addition, a truly nondescript shell that runs along the east side of the original building and opens to Carolina Street. The addition’s only design attribute is deference; it sits far enough back from 16th Street to not crowd the original factory’s smooth concrete curves.

A contrasting color scheme is seen on the McClintock Building at 1400 16th Street on Monday, March 7, 2016 in San Francisco, California.

Photo: Lea Suzuki Lea Suzuki, The Chronicle

Pfau Long emphasized the contrast by painting the original Art Deco structure white and the 1957 annex a rich blue-gray. Inside, though, the changes cut deep.

The best example of this is the commons, a courtyard-like atrium beneath a lean steel frame holding folds of glass that part slowly when a switch is flicked or when the interior gets too warm. It’s a fairly standard greenhouse system, but in this setting it’s positively exotic.

You wouldn’t know the commons most recently held dress racks as a windowless storage area with white plastered walls and a sturdy wood roof. The roof is gone, along with the columns that supported it. The walls have been replaced by garage-door-like openings with paneled glass, while at each end there are solid wall sections of vivid wood, the same Douglas fir that once was above.

Commons as focal point

Even when the operable roof is closed, the central courtyard feels airy and light. It also provides a visual orientation point for a building where the outer walls enclose nearly two acres of space.

“We knew we needed something distinctive in the middle as a frame of reference,” Shure said. “Our first visit to the building, for the life of me, I could not tell where I was.”

Another act of deconstruction transformed the skylit main entrance on 16th Street, within the blunt tower.

In McClintock’s heyday you encountered a wide carpeted stairway to the second floor, within billowy white walls in a postmodern echo of the smooth curves outside. Now the rococo clutter is cleared out to expose the board-framed concrete structural walls for the first time since they were erected. The new staircase is lean metal with wire railings, pulled to the rear of the space while an elevator is tucked discreetly near the entrance on the left.

The idea was not just to turn the clock back to opening day, but keep going.

“We wanted to express something that had never been expressed before,” said Dwight Long of Pfau Long, referring to the thickly textured concrete. “We were afraid when we started peeling things back that it wouldn’t be nice enough to keep exposed. Lucky for us, there really was beauty beneath the plaster.”

This isn’t the only building of the era that now exudes an aura of stripped-down cool. Even in the triumphant Pacific Telephone Building at 140 New Montgomery St., a 1925 tower clad in white terracotta, the interior has been stripped down to the bones of concrete and brick so that tenants like Yelp feel they’re roughing it.

Bridging past, future

At the McClintock Building, there’s more at work than style.

The view from the corner of 16th and Carolina streets offers a compressed-frame glimpse of today’s San Francisco. On the south side of 16th is design guru Yves Behar’s Fuseproject compound, covered in artful graffiti; across Carolina is a corrugated building that was lined with homeless tents on my visit. Beyond that there’s a block of soon-to-open apartments and then the medical zone of UCSF Mission Bay.

By keeping the 1938 structure intact, restoring its humble strength and putting McClintock’s name on proud display, there’s both continuity to the past and an investment in the future. The building helps anchor its surroundings — and these walls are tough enough to weather whatever else comes our way.

Place is a weekly column by John King, The San Francisco Chronicle’s urban design critic. Email: jking@sfchronicle.com Twitter: @johnkingsfchron

John King is The San Francisco Chronicle’s urban design critic, taking stock of everything from Salesforce Tower to public spaces and homeless navigation centers. A two-time Pulitzer Prize finalist and author of two books on San Francisco architecture, King joined The Chronicle in 1992 and covered City Hall before creating his current post in 2001. He spent the spring of 2018 as a Mellon Fellow in Urban Landscape Studies at Dumbarton Oaks in Washington, D.C.